1. Field of the Invention
The present invention relates to a method for growing a group-III nitride compound (Including BN, AlN, GaN and InN) semiconductor film, and more particularly, a method for growing a high quality group-III nitride thin film by a metal organic chemical vapor deposition (MOCVD) method, which can improve characteristics of the thin film by performing thin film growth in two steps.
2. Description of the Related Art
FIG. 1 is a vertical cross-sectional view of a GaN thin film grown by a conventional MOCVD method. As shown in FIG. 1, the GaN thin film is grown such that a GaN buffer layer 2 is first grown on a sapphire substrate 1 at 400 to 600xc2x0 C. by a MOCVD method and a GaN layer 3 is then grown thereon at 900 to 1100xc2x0 C.
The characteristics of the group-III nitride thin film grown by the MOCVD method vary according to various experimental factors. In particular, it has been found that a great change in initial growth mechanism was caused by a change in the pressure of a reactor during a growing step.
The basic characteristic of a nitride compound semiconductor device is crystallinity, which is optimized according to the type of a reactor used and experimental conditions employed by researchers. However, the researchers"" finding was that the crystallinity was deteriorated under the conditions that are advantageous to growth of multiple quantum well, p-GaN or AlGaN, e.g., a low pressure of reactor used.
To solve the above-described problems, it is an object of the present invention to provide a method for growing a high quality group-III nitride film by a metal organic chemical vapor deposition (MOCVD) method, by which the crystallinity and surface morphology of the film can be improved by a multi-step growth method in which the pressure of a reactor is changed.
To accomplish the above object, there is provided a method for growing a high quality group-III nitride film on a substrate by a metal organic chemical vapor deposition method, including the steps of forming a group-III nitride buffer layer on the substrate, forming a first group-III nitride film on the group-III nitride buffer layer by increasing the internal pressure of a reactor to a predetermined level or greater, and forming a second group-III nitride film on the first group-III nitride film by decreasing the internal pressure of a reactor to a predetermined level or below, which is lower than that for growth of the first group-III nitride film.
In the present invention, the substrate is preferably a sapphire substrate, a silicon substrate or a GaAs substrate, and the nitride buffer layer is preferably formed of AlxGa1xe2x88x92xN (0xe2x89xa6xxe2x89xa61) or InxGa1xe2x88x92xN(0xe2x89xa6xxe2x89xa61).
Also, the first and second group-III nitride films are preferably formed of is GaN-based nitride. Preferably, the first group-III nitride film is grown under the pressure in the range of 150 to 400 Torr, and the second group-III nitride film is grown under the pressure in the range of 50 to 150 Torr.